Advanced Materials

Cover image for Advanced Materials

June 1994

Volume 6, Issue 6

Pages fmi–fmi, 433–518

  1. Masthead

    1. Top of page
    2. Masthead
    3. Essay
    4. Reviews
    5. Communications
    6. Research News
    7. Talking Point
    8. Research News
    9. Book Reviews
    10. Materials Forum
    1. Masthead (page fmi)

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060601

  2. Essay

    1. Top of page
    2. Masthead
    3. Essay
    4. Reviews
    5. Communications
    6. Research News
    7. Talking Point
    8. Research News
    9. Book Reviews
    10. Materials Forum
    1. New European Funding Opportunities for Materials Research (pages 433–436)

      Dr. Ingo Hussla and Natasha Us

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060602

      Funding oopportunities in Europe are changing as the Third Framework Progamme comes to an end and the preparation of the Forth Programme nears completion. Following a brief look back at how specific workprogrammes such as Brite-Euram II and ESPRIT were organized under Framework III, details are given of how the 12.3 BECU availabel are expected to be allocated to the various activities of Framework IV. In particular, specific opportunities for materials research are listed in the areas of information technologies and industrial technologies.

  3. Reviews

    1. Top of page
    2. Masthead
    3. Essay
    4. Reviews
    5. Communications
    6. Research News
    7. Talking Point
    8. Research News
    9. Book Reviews
    10. Materials Forum
    1. Oligomeric Tetrathiafulvalenes: Extended donors for increasing the dimensionality of electrical conduction (pages 439–459)

      Dr. Martin Adam and Prof. Klaus Müllen

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060603

      Novel monomeric, oligomeric, and polymeric charge-transfer complexes with interesting electrical conductivity properties and even exhibiting superconductivity are expected to be obtainable by the systematic chemical modification of extended tetrathiafulvalenes (see Figure for one example). The synthesis and cyclic voltammetric characterization of such extended donors are reviewed in detail.

    2. BiSrCaCuO High-Tc Superconductors (pages 460–469)

      Dr. Peter Majewski

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060604

      High-Tc superconductivity in the Bi-Sr-Ca-Cu Osystem was discovered six years ago. Since then the superconducting compounds have been indentified and their structures, crystal chemistry, phase equilibria, and properties investigated extensively. Recent results of studies of the crystal chemistry and phase equilibria of these challenging materials are presented and discussed. Possible areas for future work, where knowledge is lacking or measurements are contradictory, are pointed out.

  4. Communications

    1. Top of page
    2. Masthead
    3. Essay
    4. Reviews
    5. Communications
    6. Research News
    7. Talking Point
    8. Research News
    9. Book Reviews
    10. Materials Forum
    1. Pyrazaboles: New room-temperature columnar liquid crystals (pages 470–472)

      Dr. Joaquím Barberá, Raquel Giménez and Dr. José Luis Serrano

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060605

      A nove approach to mesomorphism is reported in which discotic pyrazole derivatives are formed by dimerization of half-disk-shaped promesogenic pyrazoles throught BH2 bridges. The figure show the texture of the Dhd mesophase exhibited by one of the resulting pyrazoboles. How the mesomorphism is affected by the number and position of peripheral chains is alos described.

    2. In-situ stress investigations on thin copper films with the STM (pages 473–476)

      Dr. Thomas Fries, Dr. Klaus Oster and Dr. Klaus Wandelt

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060606

      High-resolution analysis of stress phenomena at surface can be carried out using a scanning tunneling microscope fitted with a sample holder that permits microsopic three-point bending experiments. to demonstrate the reported. It is shown that details of the recovery porcesses are revealed by the root mean square surface roughness while recrystallization can be directly observed as structural changes. The rate of transport of material is also evaluated.

    3. Surface nano-topography of drawn polyethylene and its modification using scanning force microscopy (pages 476–480)

      Alexander Wawkuschewski, Prof. Hans-Joachim Cantow and Dr. Sergei N. Magonov

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060607

      Scanning force microscopy (SFM) of oriented polyethylene reveals additional structural details that are not accessible by other techniques. For example, the Figure show that, in addition to the main fibrillar features, there exist nanofibrils oriented perpendicular to the stretching direction. The unique contribution of SFM result to studies of the structural hierarchy of oriented polymers is discussed.

    4. Homogeneous dispersion of nanostructured aluminum nitride in a polyimide matrix (pages 481–484)

      Dr. Xiaohe Chen, Dr. Kenneth E. Gonsalves, Dr. Gan-Moog Chow and Dr. Tongsan D. Xiao

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060608

      Advanced polymer/nanoparticle composites are currently of great interest because of their unique properties. The bulk properties of these materials are strongly influenced by the nature of the ultrafine filler particles–including their dispersion. A technique is presented for the de-agglomeration of chemically synthesized aluminum nitride nanoparticles and their uniforn dispersion in a polymer matrix. Detrailed mechanisms for the de-agglomeration are discussed as topics for future investigation.

    5. New polyether-based ionoselective materials (pages 484–486)

      Dr. Branko Dunjic, Dr. Alain Favre-Réguillon, Dr. Olivier Duclaux and Prof. Marc Lemaire

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060609

      The need to separate metalions form various media has led to a demand for ionoselective materials. One approach is to attach specific ligands to a polymeric carrier. The synthesis of the monomer show and its polymeriztion by tow different methods are reported. The cation bingding properties of the resulting polyether-supported macrocycles as determined by competitive extraction of five alkali metal cations are described.

    6. Magnetic dipole and electric quadrupole contributions to second-harmonic generation in C60—A valence effective hamiltonian study (pages 486–488)

      Dr. Zhigang Shuai and Prof. Jean-Luc Brédas

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060610

      The nonlinear optical (NLO) properties of fullerenes have attracted great attention recently. However, there is no agreement on the origin of the second-harmonic generation (SHG) signla, for example. The work reported here could settle this dispute. A theoretical approach to calculating the electric-dipole, magnetic-dipole, and electic-quadrupole transition moments SHG spectra in C60 are calculated.

    7. Green Electroluminescence in Poly-(3-cyclohexylthiophene) light-emitting diodes (pages 488–490)

      Magnus Berggren, Dr. Göran Gustafsson, Dr. Olle Inganäs, Mats R. Andersson, Dr. Olof Wennerström and Prof. Thomas Hjertberg

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060611

      Electoluminescent devices based on polythiophene-system this films have been demonstrated that together span the entire visible range, steric hindrance being used to vary the bandgap between compunds. Poly-(3-cyclohexylthiophene), see Figures, exhibits green electoluminescence. Possible interpretations of this observation are proposed.

    8. Angular Dependence of the Emission from a Conjugated Polymer Light-Emitting Diode: Implications for efficiency calculations (pages 491–494)

      Neil C. Greenham, Dr. Richard H. Friend and Dr. Donal D. C. Bradley

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060612

      The ability to compare electroluminescence efficiencies is important now that light-emitting diodes (LEDs) have been constructed using many different polymers and different device structures. Various ways of defining and measuring the efficiency of polymer LEDs are discussed, revealing the need to understand the nature and orgin of the angular dependence of the emission. A model for the angular distribution of the emitted light is proposed and measurements of the ligh output of a polymer LED described whose results are consitent with the model.

    9. Large second-order optical nonlinearities and enhanced thermal stabilities in extended thiophene-containing compounds (pages 494–496)

      Dr. Sandra Gilmour, Dr. Seth R. Marder, Dr. Joseph W. Perry and Dr. Lap-Tak Cheng

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060613

      The optimiztion of second order optical nonliearity requires molecules with a specific degree of ground-state polarization. In this connection, studies of extended thiophne-containing compunds with acceptors that gain aromaticity on charge separation, such as the molecule shown, are described. As it also exhibits good therma stability, this compound is a promising candidate for electro-optic poled polymer applications.

  5. Research News

    1. Top of page
    2. Masthead
    3. Essay
    4. Reviews
    5. Communications
    6. Research News
    7. Talking Point
    8. Research News
    9. Book Reviews
    10. Materials Forum
    1. Synthesis of covalent carbon—nitride solids: Alternatives to diamond? (pages 497–499)

      Prof. Charles M. Lieber and Dr. Z. John Zhang

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060614

      Covalent carbon nitride has been produced for the first time. Binary carbon-nitrogen solids are an important synthetic goal, since although β-C3N4, has been predicted to have a hardness comparable to or greater than diamond, it cannot be produced by traditional solid-state chemistry methods. The novel approach described here combines pulsed laser ablation with a high-flux atomic beam. From comparisons with calculated diffraction patterns, it is inferred that crystalline β-C3N4, has been synthesized, although in an impure form.

    2. Membranes exhibiting molecular recognition (pages 500–502)

      Prof. Clement H. Bamford and Dr. Kadem G. Al-Lamee

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060615

      Membranes with molecular recognition properties find applications in affinity separations and immunodiagnosis. The Figure illustrates the structure typical of the electrostatically spun polymer membranes considered here. The natural species that can be attached to a membrane–and their uses–are described, and it is shown that completely synthetic systems are useful for studying the details of the recognition process.

    3. Permeation Properties of Liquid Crystal—polymer composite membranes (pages 503–506)

      Prof. Rita B. Blumstein and Dr. Jo Ann Ratto

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060616

      The transport properties of membranes containing liquid crystals (LCs) are discussed and several examples presented that illustrate the potential of such membranes with and without a specific transport component. The thermal response, i.e. the influence of the LC phase transition on the permeability, and the effect of electric fields are described. It is shown that members of this unique family of membranes display the high flux characteristic of fluids above the mesophase transition temperature while retaining excellent mechanical properties.

    4. The observation of polymer reptation (pages 507–509)

      Prof. Erich Sackmann, Dr. Josef Käs and Dr. Helmut Strey

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060617

  6. Talking Point

    1. Top of page
    2. Masthead
    3. Essay
    4. Reviews
    5. Communications
    6. Research News
    7. Talking Point
    8. Research News
    9. Book Reviews
    10. Materials Forum
    1. Polar orientation of inorganic anionic groups in the crystal lattice (pages 510–511)

      Younan Xia

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060618

      The search for nonlinear optical (NLO) materials continues. Many methods are known for producing oriented structures of organic molecules, e.g., self-assembly and templating, but these do not work for inorganic materials. A formula is introduced that acts as a guideline for the synthesis of novel inorganic NLO borate materials and the properties of the first compound synthesized on the basis of this formula, SrBe2(BO3)2, are reported. It is expected that this work can be extended to other inorganic anionic groups.

  7. Research News

    1. Top of page
    2. Masthead
    3. Essay
    4. Reviews
    5. Communications
    6. Research News
    7. Talking Point
    8. Research News
    9. Book Reviews
    10. Materials Forum
    1. Photoinitiated Electron Transfer in Synthetic Model Systems (pages 512–516)

      Prof. Daniel L. Akins and Dr. Chu Guo

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060619

      Studies of electon transfer (ET) have enhanced our understanding of photosynthetic and photobiochemical systems in recent years, but much remains to be learnt. In particular, the connection between the arthitecture of the photosynthetic reaction center and its function needs to be investigated, Raman scattering studies are presented on model ET systems–covalently linked porphyrin-methylviologen and porphyrin-dibenzylviologen–in which the doner and acceptor are kept in a well-defined geometry, and the conclusions that can be drawn are discussed.

  8. Book Reviews

    1. Top of page
    2. Masthead
    3. Essay
    4. Reviews
    5. Communications
    6. Research News
    7. Talking Point
    8. Research News
    9. Book Reviews
    10. Materials Forum
  9. Materials Forum

    1. Top of page
    2. Masthead
    3. Essay
    4. Reviews
    5. Communications
    6. Research News
    7. Talking Point
    8. Research News
    9. Book Reviews
    10. Materials Forum
    1. Materials Forum (page 518)

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060623

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